Utilization of Wetlands by Ardeids in Starling Inlet, Hong Kong: A Year-Round Study and a Comparison between the Census and Flight-Line Methods

Abstract

-Habitat use by ardeids in Starling Inlet, Hong Kong, was assessed by walking a fixed 6 km route, two or three times a month, during low tide between August 1997 and August 1998. A total of 36 surveys were made, with a mean count of 452 individuals per survey (S.E. ? 128). Eight species of ardeids and two species of bitterns were recorded. In the winter, non-breeding season, the dominant species was the Great Egret (Casmerodius albus), while in the summer (breeding season) it was the Black-crowned Night Heron (Nycticorax nycticorax). Shallow coastal waters and mudflats were the most important habitats at low tide for Great and Little Egrets (Egretta garzetta), and Grey Herons (Ardea cinerea), while fishponds were the most important for Black-crowned Night Herons. A freshwater marsh was used mainly by Cattle Egrets (Bubulcus ibis) and Intermediate Egrets (Mesophoyx intermedia). During the 1998 breeding season, a comparison was made between the census and a flight-line methods in evaluating ardeid habitat use. Both methods gave similar results for habitat use by Great and Little Egrets, but the census method underestimated the use of mangrove habitats by Black-crowned Night Herons and missed the use of wet grassland habitats outside the inlet by Cattle Egrets. We suggest that the census method is more efficient for assessing the use of particular open habitats, while the flight-line method is more accurate for investigating overall use of a landscape during the breeding season. Received 2 August 2000, accepted 30 December 2000.